1. Field of the Invention
This invention relates to methods and apparatus for the medical treatment of disease of the heart. More particularly, this invention relates to a method and apparatus for treating cardiac arrhythmias by ablating in a vicinity of pulmonary venous tissue using radiofrequency energy.
2. Description of the Related Art
Invasive cardiac ablation techniques are well-known in the art. For example, U.S. Pat. Nos. 5,443,489, 5,480,422 and 5,954,665 to Ben-Haim describe systems for ablating cardiac tissue. U.S. Pat. No. 5,807,395 to Mulier et al., and U.S. Pat. No. 6,190,382 to Ormsby et al., describe systems for ablating body tissue using radio frequency. U.S. Pat. Nos. 6,251,109 and 6,090,084 to Hassett et al., U.S. Pat. No. 6,117,101 to Diederich et al., U.S. Pat. Nos. 5,938,660 and 6,235,025 to Swartz et al., U.S. Pat. No. 6,245,064 to Lesh et al., U.S. Pat. Nos. 6,164,283, 6,305,378 and 5,971,983 to Lesh, U.S. Pat. No. 6,004,269 to Crowley et al., and U.S. Pat. No. 6,064,902 to Haissaguerre et al., describe apparatus for tissue ablation to treat atrial arrhythmia, primarily by ablating tissue located within the pulmonary veins or on the ostia of the pulmonary veins. U.S. Pat. No. 5,366,490 to Edwards et al. describes a method for applying destructive energy to a target tissue using a catheter.
More recently, circumferential lesions at or near the ostia of the pulmonary veins have been created to treat atrial arrhythmias. U.S. Pat. Nos. 6,012,457 and 6,024,740, both to Lesh, disclose a radially expandable ablation device, which includes a radiofrequency electrode. Using this device, it is proposed to deliver radiofrequency energy to the pulmonary veins in order to establish a circumferential conduction block, thereby electrically isolating the pulmonary veins from the left atrium.
Radiofrequency ablation using multiple contiguous circumferential points, guided by electro-anatomical mapping is proposed in the document, Circumferential Radiofrequency Ablation of Pulmonary Vein Ostia: A New Anatomic Approach for Curing Atrial Fibrillation, Pappone C, et al., Circulation 102:2619-2628 (2000).
It has also been proposed to produce circumferential ablative lesions using ultrasound delivered through a balloon. This technique is described, for example, in the document, First Human Experience With Pulmonary Vein Isolation Using a Through-the-Balloon Circumferential Ultrasound Ablation System for Recurrent Atrial Fibrillation, Natale A, et al., Circulation 102:1879-1882 (2000).
PCT Publication WO 02/30331 to Walsh et al. describes a stent device that is geometrically adapted to irradiate an area that is confined primarily to the vascular endothelium, in order to ablate hyperplastic tissue growing around the stent. Radiation by the stent occurs when it is subjected to a RF field produced by an external scanner. Repeated ablation by this device is said to prevent blockage of the stent.